ARTS_ twenty million two hundred and twenty thousand six hundred and twenty-eight

ARTS The first 1 Zhou

One per week ARTS： Algorithm： Do one every week leetcode The algorithm of Review： Read and comment on writing an English technical article Tip： Learn at least one technical skill Share： Share a technical article with ideas and thoughts .

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Table of Contents

• Algorithm Two points search
• Review JVM Reading guide ——— explain Java Virtual machine architecture
• Tip Regular expressions , Replace spaces and comments
• Share Computer science course recommendation

Algorithm

704. Two points search

Title Description ： Given a  n  The elements are ordered （ Ascending ） integer array  nums And a target value  target  , Write a function search  nums  Medium target, If the target value has a return subscript , Otherwise return to -1.

public class  Two points search _704 {
    public static void main(String[] args) {
        int[] nums = new int[]{-1,0,3,5,9,12};
        int target = 9;
        System.out.println(search(nums, target));

        nums = new int[]{-1,0,3,5,9,12};
        target = 2;
        System.out.println(search(nums, target));
    }
    
    public static int search(int[] nums, int target) {
        int left = 0, right = nums.length - 1;
        while (left <= right) {
            int mid = (right - left) / 2 + left;
            int num = nums[mid];
            if (num == target) {
                return mid;
            } else if (num > target) {
                right = mid - 1;
            } else {
                left = mid + 1;
            }
        }
        return -1;
    }
}

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 Time complexity ：O(logn), among  n Is the length of the array .
 Spatial complexity ：O(1)O(1).

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leetcode link

Review

JVM Tutorial - Java Virtual Machine Architecture Explained for Beginners

JVM Reading guide —— Explain for beginners Java Virtual machine architecture ,JVM(Java virtual machine ) yes Java The core of the ecosystem , Make the software program able to “ Write once , Run anywhere ”,JVM Originally designed to support JAVA, Later, as time goes by , Also supports the Scala、Kotlin and Groovey. In this article , The author introduces JVM Its working principle and its various components .

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What is a virtual machine ？

 A virtual machine is a virtual representation of a physical computer , A physical machine can run multiple virtual machines , Each virtual machine has its own operating system and Application , These virtual machines are isolated from each other .

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What is? Java virtual machine ？

 stay  C  and  C++  In programming languages , The code is first compiled into platform specific machine code . These languages are called compilation languages （compiled languages）.

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 On the other hand , stay  JavaScript  and  Python  Such as language , The computer executes instructions directly without compiling them . These languages are called interpretive languages （interpreted languages）.

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Java  Combine these two technologies . Java The code is first compiled into bytecode to generate a class .class file . Then this class file is composed of Java Virtual machine explains . The same class file can run on any version of any platform and operating system  JVM On the implementation .

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 Similar to virtual machines ,JVM  Create an isolated space on the host . This space can be used to perform  Java  Program , It has nothing to do with the platform or operating system of the machine 

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Java Virtual machine architecture

JVMb Include 3 Two different components ：

• Class Loader （ Class loader ）
• Runtime Memory/Data Area （ Run time memory / Data area ）
• Execution Engine （ Execution engine ） evernotecid://3E6433C6-011C-425E-8C4F-812D1500C164/appyinxiangcom/25583646/ENResource/p4600
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Class loader Class Loader

The class loading process is divided into three stages ： load (loading)、 link (linking) And initialize (initialization).

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Run time memory / Data area Runtime Memory/Data Area

There are five components in the runtime data area , Here's the picture

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Execution engine Execution Engine

Once bytecode is loaded into main memory , And the details in the runtime data area are available , The next step is to run the program . The execution engine handles this problem by executing the code that exists in each class .

however , Before executing the program , Need to convert bytecode into machine language instructions . JVM You can use an interpreter for the execution engine （Interpreter） or JIT compiler .

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Java Native Interface (JNI)

Java Supported by Java Native interface (JNI) Execute native code .

Native method library （Native Method Libraries） Using other programming languages （ for example C、C++ And assembly language ） Authored Library . These libraries are usually in the form of .dll or .so The form of the document exists . These local libraries can be accessed through JNI load .

summary ：

The author discusses Java The architecture of virtual machine and its various components . Usually we don't delve into JVM Internal mechanism , It doesn't care how the code works when it runs . Only when there is a problem and we need to adjust JVM Or repair memory leaks , We will try to understand its internal mechanism .

This is also a very popular interview question , Whether it's a junior or senior back-end position . Deepen understanding JVM It can help you write better code and avoid the pitfalls associated with stack and memory errors .

Tip

Use VS code perhaps IDEA when , If you need to delete comments or spaces in the code , You can use the following regular expression

// Format notes , Regular expressions 
(/\*([^*]|[\r\n]|(\*+([^*/]|[\r\n])))*\*+/|[ \t]*//.*)
 Blank line , The rules are as follows 
^\s*(?=\r?$)\n

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